1. Field of the Invention
The invention relates to a continuously working press, and, more particularly, to a continuously working press for the production of chipboards, fiberboard, plastic boards, plywood boards or the like.
2. Discussion of the Related Art
Such presses typically include flexible, endless steel bands which transmit the pressing force and draw the article to be pressed through the press and which are supported with an adjustable press nip against abutments of press platen and press ram via co-rotating rolling rods guided with their axes transverse relative to the running direction of the band. The rolling rods are typically introduced in the entry region orthogonally relative to the longitudinal center of the press and into the pressing region by plate-link chains and by introduction devices.
A press of the type mentioned is described in German patent specification No. 3,152,911. In this press, the introduction device consists of a plurality of rotating roller chains which are distributed at a distance from one another over the width of the sheet-steel press bands, the rolling rods being mounted in the entry region in the manner of rolling bearings on the rollers of the roller chains.
A disadvantage of this rolling-rod introduction device is that, when there is a permanent positive alignment of the rolling rods at an exact distance from one another, an overloading of the roller chains and consequently a differing extension of the chain plate links occur. This in turn means that the rolling rods are no longer at an exact distance from one another on entry into the high-pressure region, which could result in a run-on of the rolling rods and their destruction. Furthermore, the directing forces of the rollers acting permanently on the rolling rods cause a partial wear on the rolling rods and in the joints of the roller chains. The wear in the joints results in a greater play. But, because of this, an exact alignment of the rolling rods at a predetermined spacing is lost once again, since, with increasing age, the roller chains have a different pitch division. Therefore, the alignment of the rolling rods with an exact gap spacing depends on the counterpressure arising from the article to be pressed.
Another disadvantage is that the roller chains cool during the return outside the heating plates. At different temperatures between the two outer chain introduction points on the left and right sides of the press, an orthogonal entry is then disrupted by different chain extensions. Moreover, in the positive introduction region beginning at the start of the entry tangent, the roller chains experience an elongation as a result of an increased temperature, thereby partially necessitating a higher rolling-rod speed in this region than the usual speed of 0.5 x the steel band speed. This partial acceleration likewise leads to wear on the roller chains and rolling rods, creating a further adverse effect on the surface of the pressed boards from striation.